1. The entomopathogenic nematode *Heterorhabditis* sp. is used for the biological control of which pest?
Rice stem borer
Pea leaf miner
White grub
Coriander aphid
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Correct Answer: White grub Species of *Heterorhabditis* are parasitic nematodes that effectively seek out and kill soil-dwelling insect larvae. They are widely used as a biocontrol agent against white grubs (larvae of scarab beetles), a common pest in soil.
2. *Pectinophora gossypiella* is a well-known pest primarily of which crop?
Cumin
Brinjal
Cotton
Spinach
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Correct Answer: Cotton *Pectinophora gossypiella*, commonly known as the Pink Bollworm, is a major and highly destructive insect pest of cotton crops worldwide. Its larvae damage cotton bolls, affecting yield and lint quality.
3. Which of the following is a major insect pest found in stored rice?
*Corcyra cephalonica*
*Tribolium castaneum*
*Callosobruchus* sp.
*Systole albipennis*
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Correct Answer: *Corcyra cephalonica* *Corcyra cephalonica*, the Rice Moth, is a significant pest of stored grains, particularly rice. The larvae feed on the grains and create webbing, causing considerable damage and loss during storage. *Tribolium* affects flour, *Callosobruchus* affects pulses, and *Systole* affects coriander.
4. The coefficient of correlation (r) between X and Y is 0.6, their covariance (Cov(X,Y)) is 4.8, and the variance of X (Var(X)) is 9. What is the standard deviation of Y (SD(Y))?
4.8 / (3 * 0.6)
0.6 / (4.8 * 3)
(4.8 * 0.6) / 3
4.8 / (9 * 0.6)
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Correct Answer: 4.8 / (3 * 0.6) The relationship is given by r = Cov(X,Y) / (SD(X) * SD(Y)). First, find SD(X) = sqrt(Var(X)) = sqrt(9) = 3. Then rearrange the formula: SD(Y) = Cov(X,Y) / (SD(X) * r). Substitute the values: SD(Y) = 4.8 / (3 * 0.6).
5. The mean of 20 observations is 25. If 3 is added to each observation, what will the new mean be?
26
28
30
32
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Correct Answer: 28 Adding a constant value to each observation in a dataset shifts the mean by that same constant value. Therefore, the new mean will be the original mean plus the added constant: 25 + 3 = 28.
6. Which of the following options represents a discrete variable?
Height
Time
Wages paid to workers
Number of children in a family
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Correct Answer: Number of children in a family A discrete variable can only take specific, distinct values (usually integers) and cannot take intermediate values. The number of children (0, 1, 2, ...) fits this definition. Height, time, and wages are generally considered continuous variables as they can theoretically take any value within a range.
7. If the first quartile (Q1) is 5, the second quartile (Q2/Median) is 10, and the third quartile (Q3) is 20, what is the Quartile Deviation?
15
25
7.5
30
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Correct Answer: 7.5 The Quartile Deviation (QD), or Semi-Interquartile Range, measures dispersion and is calculated as half the difference between the third and first quartiles: QD = (Q3 - Q1) / 2. So, QD = (20 - 5) / 2 = 15 / 2 = 7.5.
8. When a change in the value of one variable does not cause any change in the value of another variable, the variables are described as:
Negatively correlated
Directly correlated
Positively correlated
Independent
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Correct Answer: Independent Statistical independence means that the occurrence or value of one variable does not affect the probability or value of the other variable. Correlation (positive, negative, or direct) implies some form of relationship or association exists between the variables.
9. The average of the absolute deviations of observations from a measure of central tendency (like mean or median) is known as the:
Mean deviation
Standard deviation
Coefficient of variation
Range
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Correct Answer: Mean deviation The Mean Deviation (or Mean Absolute Deviation) calculates the average distance of each data point from the mean (or another central point), ignoring the direction (using absolute values). It provides a measure of data spread.
10. In statistics, variance is defined as:
The square root of the variation of values
The coefficient of variation of values
The reciprocal of the mean of the standard deviation
The square of the standard deviation
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Correct Answer: The square of the standard deviation Variance is a key measure of how spread out the numbers in a data set are. Mathematically, it is the average of the squared differences from the Mean, and it is equal to the square of the standard deviation (Variance = SD²).
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